We report on the first comparison of the inelastic cross section of Ni(001) surface phonons for an extended energy range with a dynamical scattering theory. Both theory and experiment indicate large modulations in the loss cross section as a function of incident energy. The intensity ratio of the S/sub 4/ and S/sub 6/ surface phonons on Ni(001) is best fitted with a 1.7%--3.3% contraction in the outermost interlayer spacing.